My personal philosophy on the subject of rules interpretation typically follows two simple guidelines -
1) KISS - keep it simple (don't be silly)
2) When in doubt be conservative
I am somewhat amazed at the FAQs that GW are releasing now. To me it's very impressive and I have never seen this level of response from them before. I think they are really cleaning up their act. It's amazing and I love it. It has been needed for a long time in my opinion.
I am a TO for a GT and invariably I will be asked to make the call on some controversial issues. I have been a TO for several years now and I've made my fair share of mistakes. One thing I can say without a doubt is that RAW is not always right. You can abuse the rules using RAW... I have seen it happen many times. In reality all rules are based on the background for the game... It is what it is.
One thing I do when there is a tough call is perform a lot of research - if you look around there are some very smart people on the Internet to draw from as a resource. I have to say I have learned a lot lately perusing Dakka Dakka's YMDC rules forum - there are some very intelligent and informed people who post there and don't have a bias in any one particular direction - I like that a lot and find it quite refreshing. Of course there are plenty of trolles there as well... We must figure out how to successfully separate the chaff from the wheat.
I feel blessed that GW just released their new FAQs one month prior to BeakyCon2... It couldn't have come at a better time. GW answered a lot of hard questions for me and that's a great thing. I can't say enough how awesome that is and I hope they keep it up.
As a TO I have found that you do not receive a lot of praise for correct interpretation of the rules but people will invariably let you know when you screw the proverbial pooch. It's just part of the job. You can elect to always play the RAW card but I find that to be somewhat of a cop out. I could quote many examples but I won't because that is not what this discussion is all about and I hope you'll appreciate that decision of mine. I am hard nosed about the rules but I am always open to intelligent unbiased discussion... I like to think I have a no nonsense approach to the rules.
In the end it really doesn't matter how great of a job GW does - there will always be some questions. Some people are never happy looking for problems where they don't exist. We have to deal with that at times and my basic approach has worked well enough for me. As a TO you have the final say and I'm not afraid to pull the trigger. That is the responsibility of the TO and we shouldn't shy away from it in my opinion. Like I said I've made some mistakes down the line - everyone who is a TO has - but we can learn from our mistakes and do a better job. Maybe one day 40k rules will be perfect like chess or checkers but I highly doubt that will ever happen... 40k is a very complex game indeed and that's a big part of the reason why I love it so much.